While Allen said he believes the second pipe fell from above, some experts have advanced another explanation. They believe poorly cemented casings -- tubes that are supposed to form solid walls down thousands of feet of the well bore -- may have been dislodged by the blast of natural gas that shot up out of the well and above the sea floor.

If that's what happened, the piece of pipe would have gone into the blowout preventer, the 450-ton tower of valves and pistons that sits on top of the well head and is supposed to shut off the well in an emergency. The Deepwater Horizon's blowout preventer failed to cut through the pipe that ran through it, and subsequent efforts to shut the so-called shear rams using remote-control submarine robots also failed.

Preliminary investigations have shown that other questionable decisions and well-design choices precipitated the blowout of a well that had been considered a "nightmare" by BP engineers. But the blowout preventer was the last-ditch way to save the rig from the explosions that killed 11 men and eventually led to the interminable leak.

Webmaster's Commentary:

This second drill pipe was being discussed here on the blogs more than a week ago, but was only officially acknowledged Friday.